GEOLOGY OF OLYMPIC NATIONAL PARK:
PART Il NOTES ON THE GEOLOGY

Deer Park - Blue Mountain

STOP 5:
Deer Park Road

The banks
of the Deer Park Road clearly reveal the layers, or beds, of stratified
rock. Etched in relief, they form a decorative wall along the road almost
all the way to Deer Park. In many places a regular alternation of light-gray
sandstone with dark-gray to black shale is conspicuous; the sandstone
beds are hard and angular on the edges and project farther than the
softer, darker, somewhat crumbly shale beds (fig. FT 11). These are
rocks formed from sand and mud deposited in the ocean about 40 to 60
million years ago.

On broken
surfaces of the sandstone, the sand grains can easily be seen. The much
finer grains of the black shale are less easily recognized but the dust
produced from a scratched piece of shale is nothing more than dried
mud.

At 5.9
miles from the park boundary, where the road begins to break out into
the open,thicker beds of sandstone appear. In fact, the road becomes
quite rough here and just a little steeper, reflecting the greater difficulty
of making a roadcut through these hard beds. High on the mountainside
they form conspicuous ribs. A close look at the rocks reveals small,
rounded pebbles in the conglomeratic
sandstone, remnants of ancient gravels.